To save energy more and more drives which were previously driven mechanically or hydraulically are being electrified to be able to utilize the better efficiency of electric motors. Such an electrification is also underway in construction machinery such as concrete mixer vehicles, earth-moving machinery and mining machinery such as surface miners or cranes such as container bridge cranes, even though electric drives and their components can be used less easily than with work machines used in buildings due to rough working conditions such as dust exposure, powerful vibrations and the like.
In order not only to be able to utilize the better efficiency of electric motors themselves in such electric drive systems, but also furthermore to be able to save energy, electrical energy is buffered when it arises in the work cycle, for example on a lowering of loads or on braking, and is released again when energy is required, for example on the raising of loads, on accelerating, etc. The storage of the energy is sensibly brought about electrically here, for which purpose capacitors, in particular dual-layer capacitors, or other battery systems or rechargeable batteries are suited.
If such dual-layer capacitors are used as energy stores, so-called DC/DC converters or DC/DC transformers are required since the voltage over a dual-layer capacitor varies in dependence on a filling level. The named DC/DC transformer connects the dual-layer capacitor storage module to the drive elements or to the frequency inverter normally connected thereto and ensures the exchange of energy. Such DC/DC transformers or DC/DC converters designate an electric circuit which can convert a DC voltage supplied at the input into a DC voltage having a higher, lower or inverted voltage level and which is able to transfer energy from the high voltage level into the lower voltage level, for example to charge the energy storage block, and likewise to transfer energy in the other direction, e.g. to withdraw it, or to transfer it from the storage block into the DC voltage circuit of the drive system.
The linking of such an energy storage apparatus having a dual-layer capacitor to the respective drive system is, however, more or less complex and/or expensive since the individual modules of such an energy storage apparatus typically have to be laboriously configured together and have to be adapted to the framework conditions of the drive system, for example to its electric motor and power electronics. In this respect, a user or an application engineer is as a rule forced to deal with the complex internal routines in the energy store and in the DC/DC converter to be able to make the necessary designs with respect to the modules and to the internal operation. In addition, there is cabling work, which is more or less complex and/or expensive depending on the drive and the used unit, including high-current lines, bus wiring and SPS signals. At the same time, care must be taken with the initially named used unit that the energy storage apparatus has to withstand the rough operating conditions such as dust exposure and impact loads and vibration loads.
Starting from this, it is the underlying object of the present invention to provide an improved energy storage apparatus of the initially named kind as well as an improved drive system having such an energy storage apparatus, to avoid the disadvantages of the prior art and to further develop the latter in an advantageous manner. The linking of the energy storage apparatus to a respective drive system should in particular be dramatically simplified and in this respect the buffering and subsequent output of the electrical energy into and out of the energy store should nevertheless be designed efficiently and reliably.
The named object is achieved in accordance with the invention by the claimed energy storage apparatus and by the claimed drive system having such an energy storage. The use of such a drive system in a lifting apparatus and in a construction machine is furthermore a subject of the invention.
It is therefore proposed to combine the electric components of the energy storage apparatus to a plug-and-play module which can be simply connected by user in the manner of a black box to the power electronics or to the DC voltage circuit for supplying the drive system and which itself adapts to the circumstances of the system environment or carries out the required control adaptations. In accordance with the invention, the energy storage unit is characterized in that the DC/DC converter is bidirectional, the control unit has output and feed control means for controlling the DC/DC converter both on the outputting of power from the storage block to the DC voltage circuit and on the feeding of power from the DC voltage circuit into the storage block, and the named DC/DC converter, the storage block and the control unit are combined into an energy storage unit having a common housing in which the DC/DC converter, the storage block and the control unit are received and at whose outer side two connections are provided for connecting to the DC voltage circuit. Both the feed and the output of power into or out of the storage block therefore take place via the DC/DC converter which controls both the power output and the feed so that a simple link to the DC voltage circuit of the drive system is possible. In this respect, the energy storage apparatus forms an integral overall system which combines the participating and required components in a single housing into which the control for the energy management is also installed. Only the two connections present at the outer housing side essentially have to be connected to the DC voltage circuit of the drive system, wherein the control unit in the interior of the housing of the energy storage apparatus adapts the required control and regulation parameters to the drive system.
The storage block of the energy storage apparatus can in particular comprise at least one capacitor, optionally in the form of a dual-layer capacitor, for energy storage, wherein in principle, however, at least one battery or rechargeable battery can also be provided in addition or alternatively to such one or more capacitors.
To avoid thermal problems of the energy storage apparatus, the at least one storage block and/or the DC/DC converter and/or the control unit can be connected in the interior of the common housing to a cooling circuit which can optionally have coolant connections at the housing for connection to an external cooling circuit to lead the heat entering into the coolant out of the storage block and/or the DC/DC converter and/or the control unit from the housing and to be able to output it externally. To allow a simple assembly, the named coolant connections can be configured as pluggable so that only the coolant lines of the external cooling circuit have to be connected to the housing of the energy storage apparatus.
The internal and/or external cooling circuit and its components such as coolant circulators, cooling air fans, switchover valves, flow controllers and the like are controlled by the control unit in the interior of the energy storage apparatus in dependence on the temperature, in particular in dependence on the temperature of a component in the interior of the housing of the energy storage apparatus and/or on an environmental temperature. For this purpose, at least one temperature sensor can be provided and can be connectable to the control unit, said temperature sensor measuring the named component temperature and/or environmental temperature and/or the temperature of the housing interior. Alternatively or additionally, the control unit can be connectable to a flowmeter to be able to regulate the flow quantity of the cooling medium.
To be able not only to simply plug the coolant lines to the housing, the electric connections and/or the signal connections of the energy storage apparatus can also be formed as pluggable or as plugs at the outer side of the housing so that the corresponding power lines or signal lines only have to be plugged in.
To allow a simple handling and a simple transport of the energy storage apparatus, the housing into which the components of the module are integrated can be formed as divisible and can comprise a plurality of housing parts which can be put together to form a common housing into which at least the DC/DC converter, the storage block and the control unit are integrated. Different electrical components which can be connected to one another by releasable connection means, in particular plug-in contacts, on the putting together of the housing parts can be accommodated in the different housing parts. For example, plug connection parts can be attached to the interfaces of the housing parts or elsewhere such that, on the putting together or joining together of two housing parts, the plug-in connections are automatically also closed or come into engagement to connect together the electronic components which are accommodated in the two housing parts.
To ensure a secure, safe use of the energy storage unit, a warning signal device can be provided in a further development of the invention to output a warning signal when the energy storage unit is still charged with energy and in this respect voltage can still be applied at the outer connection contacts and thus a possible dangerous potential is present. The warning signal device can, for example, be visually configured and can provide a warning signal visible from the outside, but can optionally also work acoustically or in another manner.
Alternatively or additionally to such a warning signal device, an electrical disconnect switch can advantageously also be provided for disconnecting the storage block and/or for deenergizing the connections at the housing, wherein the named disconnect switch can be formed internally or in the interior of the housing of the energy storage unit as a disconnect circuit. The connections led out of the energy storage system can be deenergized voltage-wise with the aid of such an electric disconnect switch, whereby the danger potential is considerably reduced.
Alternatively or additionally, the energy storage apparatus can also comprise an integrated discharge circuit which can advantageously be actuable from the outside or can convert the energy still contained in the storage block into heat on a command from the outside. Accordingly, the storage block can be discharged by a control signal which can be given to the energy storage unit from the outside, for example wen the energy storage apparatus should be decoupled from the drive system.
The housing can advantageously be formed in a sufficiently high IP safety class which allows the use of the storage system outdoors. The energy storage apparatus is advantageously mechanically configured such that it can also be used under high vibration loads such as occur with mobile work machines such as construction machinery and cranes or by a correspondingly strong design of the housing and/or a damping embedding of the electrical components in the housing and/or a suitable design of the electrical components themselves.
The control apparatus integrated into the energy storage unit can generally have different designs or can implement differing operating modes. The control apparatus is generally adapted to the specific properties of the storage elements of the at least one storage block in an advantageous further development of the invention and contains control means for carrying out the energy management in accordance with the specific properties of the named storage elements.
To be able to efficiently control the efficient use of the buffered energy and its feeding back into the drive system or the charging of the storage block, the control unit integrated into the energy storage unit can also determine information or operating parameters relating to the state of the energy storage unit, in particular of the storage block and/or for external use. The control system can, for example, comprise control means for determining an energy index and for providing and/or transmitting this energy index to a higher-ranking control, wherein the named energy index represents the energy available in the store.
In accordance with another advantageous further development of the invention, the integrated control apparatus can also process information coming from the outside and/or can convert control commands, for example such that the control apparatus comprises control and/or regulation means for the DC/DC converter which means, in response to a control signal, convert power values definable from the outside for the charging and/or discharging by desired value default for the regulation of the DC/DC converter.
Alternatively or additionally, the control system can be supplied from the outside with configurable parameters and can carry out a characteristic controlled operating mode on the basis of these configurable parameters fed in from the outside.
In an advantageous further development of the invention, the integrated control apparatus can comprise power control means for the regulation and/or control and/or for limiting the maximum transferable powers. Alternatively or additionally, the integrated control apparatus can comprise voltage regulation and/or control means for regulating or controlling the output voltage of the energy storage unit.
The energy storage apparatus advantageously comprises at least one voltage sensor which measures the voltages at the input and/or over the storage block. In conjunction with the previously named control or regulation means, the named voltage signal can be used to regulate the output voltage, but also to transmit corresponding measured values of the current and voltage via a communication connection to an external and/or higher-ranking control apparatus.
In an advantageous further development of the invention, the modular energy storage unit cannot only be used alone, but can rather be connected to a plurality of such energy storage units. At least two, but also more than two, energy storage units can in particular be connected in parallel, wherein in a further development of the invention a plurality of such energy storage units can be connected directly in parallel with the outwardly leading power connections, e.g. plus to plus and minus to minus. The control apparatus of the or each module is in this respect advantageously configured such that it supports such a parallel connection.
The energy storage units can in particular be equipped with a communication link which allows a communication of the energy storage units among one another or a communication of the integrated control apparatus among one another. The named communication apparatus can, for example, comprise a bus system via which the energy storage units connected in parallel can communicate with one another.
In a further development of the invention, the control apparatus of the energy storage units is provided with control means or regulating means which automatically adjust all the storage blocks to a uniform energy amount with a plurality of energy stores connected in parallel or control them accordingly.
To allow a simple linking to the drive system even on a use of a plurality of energy storage units, the plurality of energy storage units can be connected among one another to a further electric line which leads to the connection of the respective internal storage block.
On a connecting together of a plurality of energy storage units, their control apparatus can interact with one another in different manners. For example, the control apparatus can act as peers with one another and can each be directly linked to a higher-ranking control, for example via a control bus.
In an alternative further development of the invention, the control apparatus of the energy storage units coupled to one another can also act with one another in a hierarchical manner, in particular such that a control apparatus of an energy storage unit forms a higher-ranking master unit and the control apparatus of the remaining energy storage units form slave units. The master unit defines conditions and/or direct control commands for the other slave units which are then carried out in a corresponding dependency. The control apparatus acting as a master unit can in particular communicate with a higher-ranking control, whereas the control apparatus acting as a slave unit can only communicate with the named master unit. The module defined as the master unit also determines and communicates the desired value defaults for the power regulation and/or other control parameters for the other modules defined as slave units.
The control apparatus acting as a master unit can advantageously have an interface for all common industrial field buses.
The invention will be explained in more detail in the following with respect to preferred embodiments and to associated drawings.